A conventional railway locomotive includes an onboard compressed air system for operation of pneumatically powered devices such as brakes, horns, sanders and shutters. The onboard compressed air system will include a compressor, an arrangement of filters and dryers to process the compressed air, one or more compressed air reservoirs, and suitable piping and valves to direct compressed air to the various pneumatically operated devices.
The compressed air output of a railway locomotive air compressor typically includes entrained water and oil which, if not removed from the compressed air, can contaminate pneumatically operated devices. The resulting corrosion, freeze-ups, and other degradations of pneumatic apparatus operation can have severe consequences. One prominent example is reduced braking reliability and deterioration or failure of brake valves. Moreover, if maintenance personnel use unsuitable additives to deal with the oil and water content of the compressed air, they may inadvertently exacerbate the very problems they seek to remedy.
The desiccant dryers commonly used to process onboard compressed air on locomotives have often proved inadequate to the task. Locomotive design practice imposes size and space limitations which permit use of only relatively small twin tower desiccant dryers. Since the air drying capacity of such dryers is related directly to desiccant tower size, the desiccant dryers a locomotive can accommodate often may be undersized. That is, the peak compressed air demand of a train and locomotive combination can exceed the air processing capacity of the most commonly available tower type desiccant dryer the locomotive can accommodate.
As an example of the unavoidable size and space limitations encountered, air drying and processing apparatus for a locomotive must interface between inlet and outlet connection flanges which are typically separated horizontally by only 1313/16 inches. An additional space limitation is that the dryer apparatus cannot interfere with locomotive truck swing movement. These and other such space limitations preclude use of desiccant dryers with sufficient desiccant surface area to ensure the compressed air demand of the train can always be met.
This invention relates to an apparatus for removing water vapor from compressed air in a railway locomotive. Specifically, permeable membrane media is used in combination with filter media in a novel apparatus to separate the various components of the compressed air gas mixture. A characteristic of permeable membranes is that, for a given pressure differential between the opposed sides of a given membrane, different gases will pass through or permeate the membrane at different rates. Thus, by using a membrane which exhibits a relatively higher water vapor permeation rate compared to its nitrogen or oxygen permeation rate, the water vapor component of a compressed air stream can be effectively removed from the air stream by the permeation process.
The pressure difference between the compressed air stream flowing along one side of the membrane, and the lower pressure on the opposed side of the membrane, drives the permeation process. Water vapor, as well as oxygen, nitrogen and other gases from the compressed air stream, will pass through the membrane at differing rates from the high pressure side to the low pressure side. For purposes of this invention, a membrane is chosen which allows permeation of water vapor at a rate sufficiently greater than that of nitrogen or oxygen to ensure that substantially all of the water vapor can be removed from the air stream with only relatively little loss of oxygen or nitrogen, the major gas components of the compressed air stream.
The present invention, in its preferred embodiment, thus contemplates a novel and improved apparatus which utilizes permeation gas separating technology for removing moisture from the onboard compressed air required for railway locomotive operation. The invention further contemplates single or multiple stage filtering apparatus used in conjunction with permeation technology for particulate and bulk liquid capture to remove oil and particulates from the compressed air stream.
The best mode of the invention comprises a modular assembly of elongated filter and membrane elements assembled in mutually parallel relationship between a pair of spaced apart manifolds. One manifold includes inlet and outlet connection flanges located for connection to the corresponding air line connection flanges of a railway locomotive. The invention provides an air drying apparatus of superior performance characteristics and capacity for the limited space envelope typically available onboard a railway locomotive.
In addition, the apparatus of the invention provides superior structural integrity to withstand the vibration, shock or impact loads, and inertial loading which are unavoidable in the railway locomotive operating environment.
It is therefore one object of the invention to provide novel and improved air drying for the compressed air generated onboard a railway locomotive.
Another object of the invention is to provide a modular assembly of air filtering and drying elements which are sized to fit within the confines of a railway locomotive space envelope provided for compressed air drying apparatus, but which nevertheless provide superior performance, durability, service life, and capacity over prior apparatus intended for the same purpose.
A more specific object of the invention is to provide a combination permeable membrane and filter assembly by confining elongated membrane and filter elements longitudinally between a pair of spaced apart manifolds, one of which manifolds also provides connection flanges for direct connection to the corresponding air line connection flanges of a railway locomotive.
These and other objects and further advantages of the invention will be more readily appreciated upon consideration of the following detailed description, and the accompanying drawings, in which:
FIG. 1 is a schematic view of a railway locomotive compressed air system including an air dryer apparatus of the present invention;
FIG. 2 is a perspective view from the vantage point of line II--II in FIG. 1, showing one presently preferred embodiment of the air dryer of this invention;
FIG. 3 is a top plan view of the air dryer of FIG. 2 with external details removed to clearly show the internal passages indicated by phantom lines;
FIG. 4 is a sectional view taken on lines IV--IV of FIG. 2 or 3;
FIG. 5 is a sectional view taken on lines V--V of FIG. 2 or 3;
FIG. 6 is a perspective view of another presently preferred embodiment of the invention, various aspects of which are also shown in FIGS. 7-12;
FIG. 7 is a sectional view taken generally on lines VII--VII of FIG. 11;
FIG. 8 is a sectional view taken on lines VIII--VIII of FIG. 7;
FIG. 9 is a sectional view taken on lines IX--IX of FIG. 8;
FIG. 10 is a sectional view taken on lines X--X of FIG. 8,
FIG. 11 is a sectional view taken on lines XI--XI of FIG. 8; and
FIG. 12 is a sectional view taken on fines XII--XII of FIG. 8.